I'm going into first-year medicine in Liverpool in a couple of weeks. I'm not sure about other medical applicants, but when I applied I had:
A - A-level Maths
A - AS Biology
A - AS Chem
B - AS Eng Lang
Once I got through the interview and was accepted, Liverpool said I needed to achieve AB in Biology and Chemistry (in any order) for my conditional offer.
Judging from this, I'm guessing that the typical offer is AAB (for me, the third A already came from my maths). At the same time though, I would highly recommend that you aim for AAA in your AS-levels, because even with my AAAB I was only accepted into one of my four UCAS choices.
Plus, if you already have AAA in AS-level, meeting the AAB A-level conditional offer will be that much easier.